1. Field of the Invention
The present invention relates to a vibration-damping electromagnetic actuator that generates driving force of a mover in relation to a stator through energization to a coil, an active fluid-filled vibration-damping device that applies the force generated by the vibration-damping electromagnetic actuator to a fluid chamber in order to reduce vibration in an offset fashion, and an active vibration-control device that reduces vibration of a member subject to vibration-damping by the force generated by the vibration-damping electromagnetic actuator.
2. Description of the Related Art
From the past, for an active fluid-filled vibration-damping device, an active vibration-control device and the like, a vibration-damping electromagnetic actuator has been used as an actuator that generates oscillation force. For example, as Japanese Patent No. JP-B-5170545 discloses, the vibration-damping electromagnetic actuator has a structure wherein a mover is inserted in a tubular stator such that a mover is allowed to displace relative to the stator. Moreover, the stator includes a coil member having a structure wherein an outer yoke is attached to a coil, while the mover has a structure wherein the permanent magnet and the inner yoke are superposed to one another in the axial direction of the stator. Furthermore, a magnetic gap is provided in an inner tubular part of the outer yoke superposed on the inner peripheral face of the coil, so that the effect of the magnetic field formed through energization to the coil displaces the mover relative to the stator in the axial direction.
For the vibration-damping electromagnetic actuator, the frequency range wherein operation is effectively controllable is affected by the mass of the mover. Thus, weight reduction of the mover enables control of the operation at a higher frequency range, thereby making it possible to set broadly a frequency range wherein the operation is controllable.
However, adopting a smaller permanent magnet for weight reduction of the mover will reduce a force acting on the mover during the energization to the coil. This may cause difficulty in obtaining necessary oscillation force in the vibration-damping device or vibration-control device. When a thickness of the inner yoke is reduced for saving its weight, it becomes difficult to dispose the inner yoke close enough to the inner tubular part of the outer yoke where a magnetic pole is formed through the energization to the coil. As a result, a generated force of the actuator becomes small.